In Situ TEM Observation of Cooperative Grain Rotations and the Bauschinger Effect in Nanocrystalline Palladium
| Autor: | Christian Kübel, Horst Hahn, Ankush Kashiwar |
|---|---|
| Přispěvatelé: | UCL - SST/IMMC/IMAP - Materials and process engineering |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Technology
Materials science General Chemical Engineering nanocrystalline metals 02 engineering and technology Plasticity 01 natural sciences Article deformation mechanisms lcsh:Chemistry 0103 physical sciences in situ transmission electron microscopy (TEM) General Materials Science Texture (crystalline) Composite material 010302 applied physics Physics Bauschinger effect 021001 nanoscience & nanotechnology Nanocrystalline material Chemistry lcsh:QD1-999 Deformation mechanism thin films automated crystal orientation mapping in STEM (ACOM-STEM) nanomechanical behavior plasticity grain rotation Grain boundary Deformation (engineering) Dislocation 0210 nano-technology ddc:600 Engineering sciences. Technology |
| Zdroj: | Nanomaterials Nanomaterials, Vol 11, Iss 432, p 432 (2021) Volume 11 Issue 2 Nanomaterials, Vol. 11, no.2, p. 432 (2021) Nanomaterials, 11 (2), 432 |
| ISSN: | 2079-4991 |
| Popis: | We report on cooperative grain rotation accompanied by a strong Bauschinger effect in nanocrystalline (nc) palladium thin film. A thin film of nc Pd was subjected to cyclic loading–unloading using in situ TEM nanomechanics, and the evolving microstructural characteristics were investigated with ADF-STEM imaging and quantitative ACOM-STEM analysis. ADF-STEM imaging revealed a partially reversible rotation of nanosized grains with a strong out-of-plane component during cyclic loading–unloading experiments. Sets of neighboring grains were shown to rotate cooperatively, one after the other, with increasing/decreasing strain. ACOM-STEM in conjunction with these experiments provided information on the crystallographic orientation of the rotating grains at different strain levels. Local Nye tensor analysis showed significantly different geometrically necessary dislocation (GND) density evolution within grains in close proximity, confirming a locally heterogeneous deformation response. The GND density analysis revealed the formation of dislocation pile-ups at grain boundaries (GBs), indicating the generation of back stresses during unloading. A statistical analysis of the orientation changes of individual grains showed the rotation of most grains without global texture development, which fits to both dislocation- and GB sliding-based mechanisms. Overall, our quantitative in situ experimental approach explores the roles of these different deformation mechanisms operating in nanocrystalline metals during cyclic loading. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|